Bukayo Saka handed penalty duty to Havertz, who duly dispatched the spotkick for his first goal for the club.
Rice said it was a special moment: “It was emotional, for the fans, for Kai, for everyone involved, because we want him to succeed so much.
“Honestly, he works his socks off every day in training. In games he gives absolutely everything. He's had chances to score this year, hadn't scored yet, but today to slot away a penalty in that high pressure moment, shows the mindset that he's got, shows the talent he's got and his all-round performance was so special, I'm so happy for him."
Rice added: “I think you can see it every day.
“We're a young group of lads who really believe and trust in the manager. He's brought that environment into the club, and the whole energy around the place in terms of staff, the players, the fans at the Emirates, the fans here today.
“It's such a special feeling. It's really good to be a part of and like I said, that's why I came to Arsenal, It's real honour to play for this club and when there are special moments like this, it's really good."